Method and apparatus for transporting deterministic traffic in a gigabit passive optical network

ABSTRACT

A system and method are disclosed for transporting deterministic traffic in a gigabit passive optical network. A system that incorporates teachings of the present disclosure may include, for example, an Optical Line Termination (OLT) for exchanging data traffic in a Gigabit Passive Optical Network (GPON) having a controller programmed to generate a timeslot schedule for transport of a desired bandwidth of constant bit rate (CBR) data traffic by selecting one or more timeslots from periodic frame clusters operating according to a GPON Transmission Convergence (GTC) protocol. Additional embodiments are disclosed.

This application is a continuation of U.S. patent application Ser. No.14/687,503, filed Apr. 15, 2015, now U.S. Pat. No. 9,699,533, which is acontinuation of U.S. patent application Ser. No. 13/863,239, filed Apr.15, 2013, now U.S. Pat. No. 9,036,500, which is a continuation of U.S.patent application Ser. No. 12/847,889, filed Jul. 30, 2010, now U.S.Pat. No. 8,422,390, which is a continuation of U.S. patent applicationSer. No. 11/426,212, filed Jun. 23, 2006, now U.S. Pat. No. 7,768,936,all of which are herein incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to gigabit passive opticalnetworks, and more specifically to a method and apparatus fortransporting deterministic traffic in said networks.

BACKGROUND

Gigabit passive optical network (GPON) is a communications accessarchitecture recently developed by the International TelecommunicationsUnion (ITU) Study Group 15 and published as standards ITU-T G.984.1through ITU-T G.984.4.

This standard provides the flexibility for network elements in a GPONnetwork to dynamically assign timeslots in frames during an activecommunications session. Reassignment of timeslots, however, can causejitter and latency which in turn can cause undesirable interruptionsand/or inoperability of a communication session involving constant bitrate (CBR) data traffic such as voice and or video. Additionally, CBRdata traffic can be significantly interrupted during an Operations,Administrative and Management (OAM) cycle which utilizes up to twoconsecutive frames.

A need therefore arises for a method and apparatus for transportingdeterministic traffic in a GPON network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an exemplary embodiment of a portion of a Gigabit passiveoptical network (GPON) communication system;

FIGS. 2-3 depict exemplary methods operating in the GPON communicationsystem;

FIG. 4 depicts and exemplary block diagram of GTC frame and timeslotassignment according to the methods of FIGS. 2-3; and

FIG. 5 depicts an exemplary diagrammatic representation of a machine inthe form of a computer system within which a set of instructions, whenexecuted, may cause the machine to perform any one or more of themethodologies disclosed herein.

DETAILED DESCRIPTION

Embodiments in accordance with the present disclosure provide a methodand apparatus for transporting deterministic traffic in GPON networks.

In a first embodiment of the present disclosure, an Optical LineTermination (OLT) for exchanging data traffic in a Gigabit PassiveOptical Network (GPON) can have a controller programmed to generate atimeslot schedule for transport of a desired bandwidth of CBR datatraffic by selecting one or more timeslots from periodic frame clustersoperating according to a GPON Transmission Convergence (GTC) protocol.

In a second embodiment of the present disclosure, an Optical NetworkUnit (ONU) for exchanging data traffic in a Gigabit Passive OpticalNetwork (GPON) can have a controller programmed to receive a timeslotschedule from an Optical Line Termination (OLT) identifying one or moretimeslots selected by the OLT from periodic frame clusters according toa desired bandwidth of at least one among Constant Bit Rate (CBR) andnon-deterministic (ND) data traffic services associated with CBR and NDTransmission Containers (T-Conts) of the ONU, and transmit CBR and NDdata traffic of the CBR and ND T-Conts according the timeslot schedule.

In a third embodiment of the present disclosure, a method can generateat an Optical Line Termination (OLT) a schedule for transport ofConstant Bit Rate (CBR) data traffic in a Gigabit Passive OpticalNetwork (GPON), wherein the schedule identifies one or more data unitsselected by the OLT from periodic data clusters according to a desiredbandwidth of the CBR data traffic.

FIG. 1 depicts an exemplary embodiment of a portion of a Gigabit PassiveOptical Network (GPON) communication system 100. The GPON communicationsystem 100 comprises an Optical Line Termination (OLT) 102 coupled toone or more Optical Network Units (ONUs) 104 by way of one or morecommon splitters or combiners 106. The OLT 102 and ONUs 104 operateaccording to a GPON Transmission Convergence (GTC) protocol and utilizea controller comprising common computing technology for routing digitaltraffic between end points of the GPON communication system 100. Digitaltraffic can include Constant Bit Rate (CBR) traffic such as a voiceand/or video, non-deterministic traffic such as common Internet traffic,and Operations, Administrative and Management (OAM) data trafficrepresented by network management functions that provide network faultindication, ONU initialization, performance information, and data anddiagnosis functions among other things.

FIGS. 2-3 depict exemplary methods 200-300 operating in the OLT 102 ofcommunication system 100. Method 200 describes a means for selectingframes and timeslots, while method 300 depicts a complementary methodfor assigning timeslots. To reduce jitter and latency due to dynamictimeslot assignments in prior art GPON communication systems, the OLT102 can be programmed in step 202 to organize GTC frames into periodicframe clusters (PFCs) (see FIG. 4). From the PFCs the OLT 102 can beprogrammed in step 202 to select a portion of said GTC frames asreserved for CBR and non-deterministic (ND) data traffic (“User TrafficReserved Frames”) while the remaining portion of said GTC frames isavailable for ND data traffic, and Operations, Administrative andManagement (OAM) data traffic (“Residual Frames”).

In step 204, the OLT 102 selects a number (which could be zero) oftimeslots (not actual timeslot assignments) in each UTR frame for eachCBR Transmission Container (T-Cont) of the ONUs 104. The numbers oftimeslots granted to the CBR T-Conts may (and is likely to) form arepeating pattern whose period may last one or more PFCs. A T-Contrepresents a logical grouping of data ports of a corresponding ONU 104having similar service characteristics. Timeslot assignments are grantedby the OLT 102 to each T-Cont of an ONU 104. The number of timeslotsselected for a particular T-Cont can depend on a desired bandwidth foreach data traffic stream associated with the T-Cont. The OLT 102 candetermine or assume bandwidth requirements for each CBR T-Cont through avariety of means well known to artisans of ordinary skill in the art.For example, from the OLT 102 can have pre-provisioned information, orcan receive signaling information originating at any number of networkelements (including the ONUs 104) in the GPON communication system 100.

Once the UTR frames and number of timeslots have been selected for eachT-Cont, the OLT 102 can proceed in a first embodiment to step 208 whereit checks for bandwidth changes in the CBR traffic. If there is nochange, the OLT 102 continues to operate with the frame assignments, andthe numbers of timeslots selected in step 204. If on the other hand aCBR traffic change is requested or detected in step 208, the OLT 102proceeds to step 210 where it checks if there's a bandwidth limitationwith the current UTR frame assignment. This step is particularlyimportant when the CBR traffic has increased in bandwidth. If the CBRtraffic bandwidth has increased, and there's available bandwidth tosupport this change, then the OLT 102 proceeds to step 204 where itselects a greater number of timeslots. If the CBR traffic bandwidth hasbeen reduced, then the OLT 102 proceeds to step 204 where it reduces thenumber of timeslots assigned to the CBR traffic in the UTR frames.

When a bandwidth limitation is detected in step 210 in which noadditional timeslots are available to support an increase in CBRtraffic, the OLT 102 proceeds to step 212 and determines if the UTRframe selection can be changed. For example, suppose there are 24 GTCframes in a PFC with 20 of said frames (F1 through F20) assigned as UTRFrames, and 4 frames (F21 through F24) assigned to Residual Frames.Suppose further that the only system consideration is that at least 2GTC frames in each PFC must be Residual Frames. In this instance, sincethe Residual Frames do not require more than 2 GTC frames to support OAMcycles, the OLT 102 can proceed to steps 202-204 and select a new set offrames and a new number of timeslots to support the change in CBRtraffic. If instead 22 out of the 24 UTR frames in a PFC had beenpreviously assigned to UTR traffic, then the OLT 102 would have nochoice but to proceed to step 214 and reject the request to increase CBRtraffic since at least two frames must be reserved for OAM cycles.

In another embodiment, the OLT 102 can be programmed in step 206 toassign specific CBR timeslots to each UTR frame over one or more UTRframes of a PFC cycle. This step can reduce jitter by creating a staticand regular timeslot pattern for CBR traffic across multiple UTR frames.Steps 202-214 thus provide a means for defining UTR frames and ResidualFrames with dynamic timeslot assignments in one embodiment, and statictimeslot assignments in another.

FIG. 3 illustrates method 300 which describes the steps to assigntimeslots in each GTC frame of the PFCs. Method 300 begins with step 302in which the OLT 102 advances to perform timeslot assignments for thenext GTC frame. In step 304, the OLT 102 checks whether the GTC frame ithas advanced to is a UTR frame or a Residual frame. If it is a UTRframe, then in one embodiment the OLT 102 proceeds to step 306 where itobtains from step 204 the number of timeslots to be assigned in thisframe to each CBR T-Cont. In step 308, the OLT 102 uses the obtainednumbers to schedule specific timeslots in this UTR frame to CBR T-Conts.In step 314, the OLT 102 schedules the remaining timeslots (if any areavailable) to ND T-Conts. The timeslot schedule is then transmitted instep 316 to the T-Conts of the ONUs 104 which transmit CBR and NDtraffic upstream according to this schedule. The OLT 102 then proceedsto step 302 where it repeats another cycle of method 300 for a GTCframe.

Steps 306-308 assume an embodiment in which the OLT 102 does not assignstatic timeslots, but rather reserves a number of timeslots for each UTRframe. In this embodiment, timeslots are assigned dynamically for eachUTR frame. Although a dynamic assignment can cause some additionaljitter and/or latency, the flexibility to assign timeslots provides fora means to manage the operation of fiber optic equipment such as lasersto reduce the on and off cycles which can cause a loss of timeslotusage. To better manage the dynamic scheduling of timeslots for CBR andND T-Conts, steps 308 & 314 can be combined as one step to minimize thepower cycling of fiber optic lasers.

In an alternative embodiment, the OLT 102 can be programmed to proceedfrom step 304 to step 309 where it obtains from step 206 the specifictimeslots assigned to CBR T-Conts in this UTR frame. This embodimentprovides a static assignment of timeslots. Although it can have animpact on the power cycling of fiber optic lasers, it helps to reducejitter and latency for time sensitive CBR traffic. Once the CBR schedulehas been determined, the OLT 102 proceeds as before to step 314 andassigns the remaining timeslots to the ND T-Conts, and transmits in step316 the timeslot schedule to the T-Conts of the ONUs 104 which transmitCBR and ND traffic upstream according to this schedule. The OLT 102 thenproceeds to step 302 where it repeats another cycle of method 300 for aGTC frame.

Referring back to step 304, if the GTC frame in question belongs to theResidual Frames, then the OLT 102 proceeds to step 310 where it checkswhether OAM activity needs to occur. If OAM activity is not required,then the OLT 102 proceeds to step 314 where it assigns all availabletimeslots of the unused Residual Frames to the ND T-Conts, and proceedsto step 316 as described earlier. If on the other hand, OAM activity isrequired, the OLT 102 proceeds to step 312 where it blocks out timeslotsfor OAM activity. The number of timeslots can be as many as two fullframes scheduled over one or more PFC cycles. As before, the OLT 102assigns timeslots to the ND T-Conts if timeslots are available, andproceeds to step 316 to transmit the timeslot schedule to the ONUs 104.

It would be evident to an artisan with ordinary skill in the art thatthe aforementioned embodiments can be modified, reduced, or enhancedwithout departing from the scope and spirit of the claims describedbelow. For example, the OLT 102 can be programmed to select statictimeslots for time sensitive CBR traffic, and dynamically selecttimeslots for other less sensitive CBR traffic. This is but one exampleof modifications that can be applied to the present disclosure.Accordingly, the reader is directed to the claims below for a fullerunderstanding of the breadth and scope of the present disclosure.

FIG. 5 depicts an exemplary diagrammatic representation of a machine inthe form of a computer system 500 within which a set of instructions,when executed, may cause the machine to perform any one or more of themethodologies discussed above. In some embodiments, the machine operatesas a standalone device. In some embodiments, the machine may beconnected (e.g., using a network) to other machines. In a networkeddeployment, the machine may operate in the capacity of a server or aclient user machine in server-client user network environment, or as apeer machine in a peer-to-peer (or distributed) network environment.

The machine may comprise a server computer, a client user computer, apersonal computer (PC), a tablet PC, a laptop computer, a desktopcomputer, a control system, a network router, switch or bridge, or anymachine capable of executing a set of instructions (sequential orotherwise) that specify actions to be taken by that machine. It will beunderstood that a device of the present disclosure includes broadly anyelectronic device that provides voice, video or data communication.Further, while a single machine is illustrated, the term “machine” shallalso be taken to include any collection of machines that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein.

The computer system 500 may include a processor 502 (e.g., a centralprocessing unit (CPU), a graphics processing unit (GPU, or both), a mainmemory 504 and a static memory 506, which communicate with each othervia a bus 508. The computer system 500 may further include a videodisplay unit 510 (e.g., a liquid crystal display (LCD)), a flat panel, asolid state display, or a cathode ray tube (CRT)). The computer system500 may include an input device 512 (e.g., a keyboard), a cursor controldevice 514 (e.g., a mouse), a disk drive unit 516, a signal generationdevice 518 (e.g., a speaker or remote control) and a network interfacedevice 520.

The disk drive unit 516 may include a machine-readable medium 522 onwhich is stored one or more sets of instructions (e.g., software 524)embodying any one or more of the methodologies or functions describedherein, including those methods illustrated above. The instructions 524may also reside, completely or at least partially, within the mainmemory 504, the static memory 506, and/or within the processor 502during execution thereof by the computer system 500. The main memory 504and the processor 502 also may constitute machine-readable media.

Dedicated hardware implementations including, but not limited to,application specific integrated circuits, programmable logic arrays andother hardware devices can likewise be constructed to implement themethods described herein. Applications that may include the apparatusand systems of various embodiments broadly include a variety ofelectronic and computer systems. Some embodiments implement functions intwo or more specific interconnected hardware modules or devices withrelated control and data signals communicated between and through themodules, or as portions of an application-specific integrated circuit.Thus, the example system is applicable to software, firmware, andhardware implementations.

In accordance with various embodiments of the present disclosure, themethods described herein are intended for operation as software programsrunning on a computer processor. Furthermore, software implementationscan include, but not limited to, distributed processing orcomponent/object distributed processing, parallel processing, or virtualmachine processing can also be constructed to implement the methodsdescribed herein.

The present disclosure contemplates a machine readable medium containinginstructions 524, or that which receives and executes instructions 524from a propagated signal so that a device connected to a networkenvironment 526 can send or receive voice, video or data, and tocommunicate over the network 526 using the instructions 524. Theinstructions 524 may further be transmitted or received over a network526 via the network interface device 520.

While the machine-readable medium 522 is shown in an example embodimentto be a single medium, the term “machine-readable medium” should betaken to include a single medium or multiple media (e.g., a centralizedor distributed database, and/or associated caches and servers) thatstore the one or more sets of instructions. The term “machine-readablemedium” shall also be taken to include any medium that is capable ofstoring, encoding or carrying a set of instructions for execution by themachine and that cause the machine to perform any one or more of themethodologies of the present disclosure.

The term “machine-readable medium” shall accordingly be taken toinclude, but not be limited to: solid-state memories such as a memorycard or other package that houses one or more read-only (non-volatile)memories, random access memories, or other re-writable (volatile)memories; magneto-optical or optical medium such as a disk or tape; andcarrier wave signals such as a signal embodying computer instructions ina transmission medium; and/or a digital file attachment to email orother self-contained information archive or set of archives isconsidered a distribution medium equivalent to a tangible storagemedium. Accordingly, the disclosure is considered to include any one ormore of a machine-readable medium or a distribution medium, as listedherein and including art-recognized equivalents and successor media, inwhich the software implementations herein are stored.

Although the present specification describes components and functionsimplemented in the embodiments with reference to particular standardsand protocols, the disclosure is not limited to such standards andprotocols. Each of the standards for Internet and other packet switchednetwork transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP) representexamples of the state of the art. Such standards are periodicallysuperseded by faster or more efficient equivalents having essentiallythe same functions. Accordingly, replacement standards and protocolshaving the same functions are considered equivalents.

The illustrations of embodiments described herein are intended toprovide a general understanding of the structure of various embodiments,and they are not intended to serve as a complete description of all theelements and features of apparatus and systems that might make use ofthe structures described herein. Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Otherembodiments may be utilized and derived therefrom, such that structuraland logical substitutions and changes may be made without departing fromthe scope of this disclosure. Figures are also merely representationaland may not be drawn to scale. Certain proportions thereof may beexaggerated, while others may be minimized. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

Such embodiments of the inventive subject matter may be referred toherein, individually and/or collectively, by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed. Thus, although specific embodiments havebeen illustrated and described herein, it should be appreciated that anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin a single embodiment for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

The invention claimed is:
 1. A method comprising: generating, at anoptical line termination having a processor, a timeslot schedule fortransporting data; detecting a change in an amount of a particular typeof data to be transported; determining whether a change in an assignmentof a first set of timeslots and a related change in an assignment of asecond set of timeslots supports the change in the amount of theparticular type of data to be transported; and generating a new timeslotschedule in response to the detecting and the determining.
 2. The methodof claim 1, wherein the generating the new timeslot schedule compriseschanging a number of timeslots assigned to the first set of timeslotsand changing a number of timeslots assigned to the second set oftimeslots.
 3. The method of claim 2, wherein the timeslot schedulecomprises a plurality of timeslots of a periodic frame cluster.
 4. Themethod of claim 3, wherein the plurality of timeslots comprises thefirst set of timeslots and the second set of timeslots, the first set oftimeslots designated for user data traffic and the second set oftimeslots designated for management data traffic.
 5. The method of claim3, wherein the generating the new timeslot schedule comprises increasinga number of the plurality of timeslots of the periodic frame cluster. 6.The method of claim 5, wherein the increasing the number of theplurality of timeslots is in response to determining that changing thenumber of timeslots assigned to the first set of timeslots and changingthe number of timeslots assigned to the second set of timeslots does notsupport the change in the amount of the particular type of data to betransported.
 7. The method of claim 1, wherein the generating thetimeslot schedule comprises: selecting specific timeslots to create atimeslot pattern across multiple periodic frame clusters.
 8. Anapparatus comprising: a processor; and a memory to store computerprogram instructions, the computer program instructions when executed onthe processor cause the processor to perform operations comprising:generating a timeslot schedule for transporting data; detecting a changein an amount of a particular type of data to be transported; determiningwhether a change in an assignment of a first set of timeslots and arelated change in an assignment of a second set of timeslots supportsthe change in the amount of the particular type of data to betransported; and generating a new timeslot schedule in response to thedetecting and the determining.
 9. The apparatus of claim 8, wherein thegenerating the new timeslot schedule comprises changing a number oftimeslots assigned to the first set of timeslots and changing a numberof timeslots assigned to the second set of timeslots.
 10. The apparatusof claim 9, wherein the timeslot schedule comprises a plurality oftimeslots of a periodic frame cluster.
 11. The apparatus of claim 10,wherein the plurality of timeslots comprises the first set of timeslotsand the second set of timeslots, the first set of timeslots designatedfor user data traffic and the second set of timeslots designated formanagement data traffic.
 12. The apparatus of claim 10, wherein thegenerating the new timeslot schedule comprises increasing a number ofthe plurality of timeslots of the periodic frame cluster.
 13. Theapparatus of claim 12, wherein the increasing the number of theplurality of timeslots is in response to determining that changing thenumber of timeslots assigned to the first set of timeslots and changingthe number of timeslots assigned to the second set of timeslots does notsupport the change in the amount of the particular type of data to betransported.
 14. The apparatus of claim 8, wherein the generating thetimeslot schedule comprises: selecting specific timeslots to create atimeslot pattern across multiple periodic frame clusters.
 15. A computerreadable storage device storing computer program instructions, which,when executed on a processor, cause the processor to perform operationscomprising: generating a timeslot schedule for transporting data;detecting a change in an amount of a particular type of data to betransported; determining whether a change in an assignment of a firstset of timeslots and a related change in an assignment of a second setof timeslots supports the change in the amount of the particular type ofdata to be transported; and generating a new timeslot schedule inresponse to the detecting and the determining.
 16. The computer readablestorage device of claim 15, wherein the generating the new timeslotschedule comprises changing a number of timeslots assigned to the firstset of timeslots and changing a number of timeslots assigned to thesecond set of timeslots.
 17. The computer readable storage device ofclaim 16, wherein the timeslot schedule comprises a plurality oftimeslots of a periodic frame cluster.
 18. The computer readable storagedevice of claim 17, wherein the plurality of timeslots comprises thefirst set of timeslots and the second set of timeslots, the first set oftimeslots designated for user data traffic and the second set oftimeslots designated for management data traffic.
 19. The computerreadable storage device of claim 17, wherein the generating the newtimeslot schedule comprises increasing a number of the plurality oftimeslots of the periodic frame cluster.
 20. The computer readablestorage device of claim 19, wherein the increasing the number of theplurality of timeslots is in response to determining that changing thenumber of timeslots assigned to the first set of timeslots and changingthe number of timeslots assigned to the second set of timeslots does notsupport the change in the amount of the particular type of data to betransported.